The invention relates to a photometric mode switching apparatus for cameras of the automatic exposure control type, and more particularly, to such apparatus for use with a camera of the automatic exposure control type which permits a selection between an average photometry and a localized or spotwise photometry.
As is well recognized, a photometric technique utilized in the camera of the automatic exposure control type of the prior art can be categorized into an average photometry and a localized or spotwise photometry. The average photometry provides a passable result for ordinary objects being photographed, and is easier to use as compared with the spotwise photometry. In general, almost all cameras employ this technique. On the other hand, the spotwise photometry can be advantageously utilized as when it is desired to establish a desired exposure upon an object being photographed which exhibits a high contrast ratio.
Recently, a camera has been proposed having both the average and the spotwise photometry capability so that a user can suitably choose either photometric mode in taking pictures. A camera of this kind is also known in which a photometric operation in either mode is performed in interlocked relationship with a shutter release operation and in which a switching between the both photometric modes is achieved by a single mode selecting switch.
It will be understood that as a variation of the spotwise photometry, an exposure value storing photometric technique is available in which an exposure value is previously determined by a manual operation before a shutter release takes place. With the camera having the both capabilities for the average photometry and the spotwise photometry and which is designed to permit a storage of the exposure value, it is necessary when taking a picture according to the spotwise photometry method that a storage switch be operated to preset the exposure, in addition to operating the mode selecting switch. Considering the manual operation of the storage switch which is utilized during a spotwise photometric mode, it will be recognized that most objects being photographed are centrally disposed within the image field, and hence the spotwise photometry takes place of the central region of the image field. It is to be noted that a user may sometimes choose a photographic composition in which the image of a desired object being photographed be taken in a corner, for example, remote from the central region of the image field. In such instance, the camera is initially focussed to the object being photographed which is centrally located on the image field and then the storage switch is manually operated to complete the photometry of the brightness of the object being photographed. Subsequently, the camera is redirected so that the object be disposed at a desired location on the image field before a shutter release takes place. In this manner, a sophisticated photographing can be achieved which reflects the intention of the user.
Therefore, it will be seen that a camera of the automatic exposure control type which permits a free choice between the average photometry and the spotwise photometry enables a variety of pictures to be taken from the sophisticated composition to snap shots, affording a flexibility and a convenience in use.
However, a camera of the type described requires the provision of the storage switch which is manually operated during the spotwise photometry, in addition to the mode selecting switch. This induces the following difficulties:
(1) When a user of the camera desired to take a picture in the average photometric mode, he may make a wrong recognition that the average photometric mode is established in the camera when in actuality the mode selecting switch is thrown to a position corresponding to the spotwise photometric mode. If he directly releases the shutter, a wrong exposure results since the storage switch which is utilized to store exposure information is not manually operated and the camera operates in the spotwise photometric mode without exposure information.
(2) When a user of the camera desires to take a picture in the spotwise photometric mode, he may inadvertently forget that the storage switch has not been operated to store exposure information though he is aware of the fact that the mode selecting switch has been thrown to the position corresponding to the spotwise photometric mode. In this instance, a shutter release again results in a wrong exposure as mentioned above.
Thus a user of the camera may forget operating either the mode selecting switch or the storage switch. In either instance, the problem that a wrong exposure may be caused by the failure to supply exposure information during the spotwise photometric mode as a result of forgetting a switching operation before taking a picture is inherent in a camera having the capabilities for both the average and the spotwise photometry and in which an exposure control during the spotwise photometric mode takes place in accordance with a stored value of the brightness of object being photographed which is supplied through the manually operated storage switch.